Question: ${3 \div 0.4 = {?}}$
Answer: $ {3 \div 0.4 = 3 \div \dfrac{4}{10}} $ $ {\phantom{3 \div 0.4} = 3 \div \dfrac{2}{5}} $ Dividing by a fraction is the same as multiplying by the reciprocal of the fraction. $ {3 \div \dfrac{2}{5} = 3 \times \dfrac{5}{2}} $ $ {\phantom{3 \div \dfrac{2}{5}} = \dfrac{3 \times 5}{2}} $ $ {\phantom{3 \div \dfrac{2}{5}} = \dfrac{15}{2}} $ $ {\phantom{3 \div \dfrac{2}{5}} = 7.5} $